Compressor

ABSTRACT

A compressor includes a hermetic container having resonant frequency F, a compression element operable to compress refrigerant, an electric element including a shaft rotating as to drive the compression element at a predetermined operation frequency, and a rolling bearing accommodated in the hermetic container. The rolling bearing supports the shaft rotatably. The rolling element includes plural rolling elements. The predetermined operation frequency of the electric element is different from operation frequency N expressed by a following formula: N=2·F/(n·R) where n=1, 2 and R is a number of the plurality of rolling elements. This compressor is prevented from generating large noise.

TECHNICAL FIELD

The present invention relates to a compressor used for a refrigerator.

BACKGROUND ART

In a compressor including a rolling bearing, it is said that the rolling bearing preferably includes a smaller number of rolling elements in order to reduce friction for improving its efficiency.

FIG. 9 is a cross-sectional view of conventional compressor 5001 disclosed in Japanese Patent Laid-Open Publication No. 61-53474. FIGS. 10 and 11 are an enlarged view and a cross-sectional view of rolling bearing 61 of compressor 5001, respectively.

Hermetic container 1 is filled with refrigerant 3. Electric element 9 includes stator 5 and rotor 7 connected to an external power source. Hermetic container 1 accommodates electric element 9 and compression element 11 driven by electric element 9 and stores refrigerator oil 13 therein.

Compression element 11 includes shaft 21 fixed to rotor 7, cylinder block 41 providing compression space 31, and bearing 51 that is provided at cylinder block 41 and that axially supports shaft 21, thus providing a reciprocating-type compressor.

Rolling bearing 61 is provided between bearing 51 and shaft 21 via rotor 7. Rolling bearing 61 includes rolling elements 71, holder 81 for retaining rolling elements 71, and upper washer 91 and lower washer 95 which are provided at upper and lower sides of rolling element 71, respectively.

An operation of compressor 5001 will be described below.

When stator 5 is energized by the external power source, rotor 7 rotates together with shaft 21. This rotation causes refrigerant gas to be compressed in compression space 31.

Rolling bearing 61 supports a load due to weights of rotor 7 and shaft 21 in a vertical direction, and reduces a frictional force produced between rotor 7 and bearing 51. This improves an efficiency of compressor 5001.

Compressor 5001 includes rolling bearing 61 may generate a large noise at a specific frequency.

SUMMARY OF THE INVENTION

A compressor includes a hermetic container having resonant frequency F, a compression element operable to compress refrigerant, an electric element including a shaft rotating as to drive the compression element at a predetermined operation frequency, and a rolling bearing accommodated in the hermetic container. The rolling bearing supports the shaft rotatably. The rolling element includes plural rolling elements. The predetermined operation frequency of the electric element is different from operation frequency N expressed by a following formula: N=2·F/(n·R) where n=1, 2 and R is a number of the plurality of rolling elements.

This compressor is prevented from generating large noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a compressor according to Exemplary Embodiment 1 of the present invention.

FIG. 2 is an enlarged cross sectional view of the compressor according to Embodiment 1.

FIG. 3 is an enlarged view of a rolling bearing according to Embodiment 1.

FIG. 4 illustrates a noise profile of a conventional compressor.

FIG. 5 illustrates a noise profile of the compressor according, to Embodiment 1.

FIG. 6 is a cross-sectional view of a compressor according to Exemplary Embodiment 2 of the invention.

FIG. 7 is an enlarged view of a rolling bearing according to Embodiment 2.

FIG. 8 illustrates a noise profile of the compressor according to Embodiment 2.

FIG. 9 is a cross-sectional view of the conventional compressor.

FIG. 10 is an enlarged view of a conventional rolling bearing.

FIG. 11 is a cross-sectional view of the conventional rolling bearing.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Exemplary Embodiment 1

FIG. 1 is a cross-sectional view of compressor 1001 according to Exemplary Embodiment 1 of the present invention.

Hermetic container 101 accommodates electric element 109 including stator 105 and rotor 107, and compression element 111 driven by electric element 109. Electric element 109 is connected to an inverter controller. Hermetic container 101 is filled with refrigerant 103 and stores refrigerator oil 113 therein. Refrigerant 103 is R134a, HFC-based refrigerant having an ozone destruction coefficient of zero.

Rotor 107 rotates at plural frequencies by the inverter controller.

Compression element 111 includes shaft 121 fixed with rotor 107, cylinder block 141 providing compression space 131, and bearing 151 that is provided at cylinder block 141 and that axially supports shaft 121, thus providing a reciprocating-type compressor. Rolling bearing 161 is provided between bearing 151 and shaft 121.

FIG. 2 is an enlarged cross-sectional view of compressor 1001. FIG. 3 is an enlarged view of rolling bearing 161. Rolling bearing 161 includes a thrust ball bearing for supporting a vertical weight force produced by respective own weights of rotator 107 and shaft 121. Rolling bearing 161 includes eight rolling elements 171, holder 181 for retaining rolling elements 171, washer 191 provided on rolling elements 171, and washer 195 provided under rolling elements 171. Upper surface 191A of washer 191 contacts shaft 121. Lower surface 191B of washer 191 contacts rolling elements 171. Upper surface 195A of washer 195 contacts rolling elements 171. Lower surface 195B of washer 195 contacts bearing 151. Rolling bearing 161 is provided in space 101A of hermetic container 101. Rolling bearing 161 is located at the center along direction 1001B of compression in compression space 131 and at the center along direction 1001C perpendicular to direction 1001B.

An operation of compressor 1001 will be described below.

When stator 105 is energized by the inverter controller, rotor 107 rotates together with shaft 121. This rotation causes compressor 1001 to perform a predetermined compression operation for compressing gas of refrigerant 103 in compression space 131.

Rolling elements 171 of rolling bearing 161 supports a load due to weights of rotor 107 and shaft 121 in vertical direction 1001D. Upper surface 191A of washer 191 contacts shaft 121 via refrigerator oil 113. When shaft 121 rotates, the viscosity of refrigerator oil 113 causes washer 191 to rotate according to the rotation of shaft 121. Lower surface 195B of washer 195 contacts upper end portion 151A of bearing 151 via refrigerator oil 113. The viscosity of refrigerator oil 113 prevents washer 195 from rotating.

Rolling elements 171 rotates between lower surface 191B of washer 191 and upper surface 195A of washer 195 while having a rotation. Thus, rolling element 171 rotates at a rotating speed half of a rotation speed of rotor 107. A rolling friction coefficient is 1/10 to 1/20 smaller than a sliding friction coefficient. Rolling bearing 161 does not have metallic contact or adhesion so long as rolling bearing 161 has a small amount of refrigerator oil 113 attached thereto, thus rotating stably.

A noise generated in conventional compressor 5001 illustrated in FIG. 9 will be described below. A noise generated by rolling bearing 61 was analyzed. This result shows that the noise was generated by a passing vibration caused by the rotation of rolling elements 71.

The passing vibration is a vibration which is caused when one rolling element 71 passes a rough surface and vibrates. An upper surface of upper washer 91 contacts shaft 21 via refrigerator oil 13. Thus, the viscosity of refrigerator oil 13 causes shaft 21 to rotate, and upper washer 91 accordingly rotates together with shaft 21. A lower surface of lower washer 95 contacts an upper end portion of bearing 51 via refrigerator oil 13. Thus, the viscosity of refrigerator oil 13 prevents lower washer 95 from rotating. Rolling elements 71 rotates between the lower surface of upper washer 91 and the upper surface of lower washer 95 and around shaft 21 at a speed half of the rotation speed of rotor 7.

Thus, the number of rolling elements 71 that pass one point of lower washer 95 during one rotation of rotor 7 is one half of the total number of rolling elements 71. Rolling bearing 61 generates a noise having a passing vibration frequency f that is obtained by multiplying the number of rolling elements 71 passing one point by the number of rotations of rolling elements 71.

It was confirmed that, if frequencies in ranges of ±5 Hz of the frequencies of primary and secondary vibration components of the passing vibration frequency f matching with resonant frequency F of a space in hermetic container 1, a noise caused by the passing vibration was amplified and had its noise level extremely increase. The details will be described below.

FIG. 4 illustrates a noise profile of conventional compressor 5001. Compressor 5001 includes eight rolling elements 71 and rotor 7 rotating at 60 Hz, hence providing passing vibration frequency f of 240 Hz. As shown in FIG. 4, if a resonant frequency of the space in hermetic container 1 has a peak at about 480 Hz, a secondary vibration component of the passing vibration matches with the foot of a peak at the resonant frequency, hence increasing the noise.

A method of reducing a noise in compressor 1001 according to Embodiment 1 will be described below.

When rolling bearing 161 rotates, rolling elements 171 rotate and generate the passing vibration. If washer 191 or 195 has a barrier, such as a bump, rolling elements 171 contact the bump and receive a strong excitation force due to the passing vibration. This excitation force is. relatively large from the frequency of the primary vibration component to the frequency of the secondary vibration component of the passing vibration.

Vibration frequency f of the passing vibration is expressed as the relation between operation frequency N of compressor 1001 and number R of rolling elements 171 (R>1) as the following formula.

f=n·N·R/2 (where “n” is an integer)

Compressor 1001 according to Embodiment 1 operates at three operation frequencies in order to secure the maximum refrigerating capacity and to reduce power consumption. Internal space 101A of hermetic container 101 has resonant frequency F of 480 Hz. According to Embodiment 1, compressor 1001 operates at three predetermined operation frequencies of 27 r/s, 45 r/s, and 68 r/s in order that the resonant frequencies of hermetic container 101 are not provided within ranges of ±5 Hz of the frequencies of the primary and secondary vibration components of vibration frequency f of the passing vibration. That is, a predetermined operation frequency of electric element 109 is different from operation frequency N expressed as the following formula.

N=2·F/(n·R) (where n=1, 2)

This condition allows vibration frequency f of the passing vibration to be different from the frequency of the primary and secondary vibration components of resonant frequency F.

FIG. 5 illustrates a noise profile of compressor 1001 operating at an operation frequency of 45 r/s. Resonant frequency F is not within ranges of ±5 Hz of frequencies of the primary and secondary vibration components of passing vibration f, and a component of 480 Hz of the resonant frequency is not increased, thus not increasing a noise level. As a result, the passing vibration is not amplified, thus preventing compressor 1001 from generating noise.

The resonant frequency of space 101A in hermetic container 101 is determined by a length of space 101A in direction 1001B along which compression in compression space 131 is performed and by a length of space 101A in direction 1001C perpendicular to direction 1001B. Resonance in space 101A provides a node at the center of space 101A in directions 1001B and 1001C.

According to Embodiment 1, rolling bearing 161 is provided at the node of the resonance in space 101A of hermetic container 101. This arrangement prevents noise due to the passing vibration caused by rolling bearing 161 from having resonance in space 101A of hermetic container 101, thus preventing compressor 1001 from generating large noise.

According to Embodiment 1, the operation frequency of compressor 1001 is determined, so that frequencies of the primary and secondary vibration components of vibration frequency f of the passing vibration are different from the resonant frequency of hermetic container 101. Alternatively, the number of rolling elements 171 may be determined, so that a predetermined operation frequency is different from frequencies of the primary and secondary vibration components of frequency f of the passing vibration.

Although compressor 1001 of Embodiment 1 is a reciprocating type compressor, compressor 1001, but is not limited to this. Bearing 161 may be applied to compressors of arbitrary types (e.g., rotation type, scroll type, or slanting-plate type) including a rolling bearing provided at a bearing of a shaft.

Exemplary Embodiment 2

FIG. 6 is a cross-sectional view of compressor 1002 according to Exemplary Embodiment 2 of the present invention. Hermetic container 201 accommodates electric element 209 including stator 205 and rotor 207, and compression element 211 driven by electric element 209. Electric element 209 is connected to an inverter controller. Hermetic container 201 is filled with refrigerant 203 and stores refrigerator oil 213 therein. Refrigerant 203 is R600a, carbon hydride refrigerant excluding chlorine and fluorine. Rotor 207 can rotates at an arbitrary operation frequency by the inverter controller.

Compression element 211 includes shaft 221 having rotor 207 fixed thereto, cylinder block 241 providing compression space 231, bearing 251 that is provided at cylinder block 241 and that axially supports shaft 221, rolling bearing 261A press-inserted into a side of bearing towards electric element 209, and rolling bearing 261B press-inserted into a side of bearing 251 towards compression element 211, thus providing a reciprocating-type compressor. Rolling bearings 261A and 261B are both radial ball bearings for receiving a counteract force of a compressing force applied to shaft 221.

FIG. 7 is an enlarged view of rolling bearings 261A and 261B of compressor 1002. Each of rolling bearings 261A and 261B includes twelve rolling elements 271, holder 281 for retaining rolling elements 271, inner ring portion 291 provided at an inner side of arranged rolling elements 271, and outer ring portion 295 provided at an outer side of arranged rolling elements 271. Rolling elements 271 contact outer circumference surface 291A of inner ring portion 291 and inner circumference surface 295B of outer ring portion 295. Outer circumference surface 295A of outer ring portion 295 contacts bearing 251. Inner circumference surface 291B of inner ring portion 291 contacts shaft 221.

An operation of compressor 1002 will be described below.

When stator 205 is energized by the inverter controller, rotor 207 rotates together with shaft 221. This rotation causes compressor 1002 to perform a predetermined compression operation for compressing refrigerant gas in compression space 231.

At this moment, outer ring portion 295 of rolling bearing 261A does not rotate since being press-inserted into bearing 251. Shaft 221 rotates, and inner ring portion 291 accordingly rotates.

Rolling elements 271 rotate between inner ring portion 291 and outer ring portion 295 while having rotations themselves. Thus, rolling elements 271 rotate around shaft 221 at a rotating speed half of a rotating speed of rotor 207. Generally, a rolling friction coefficient is 1/10 to 1/20 smaller than a sliding friction coefficient. Rolling bearing 261 does not have metallic contact or adhesion so long as a small amount of refrigerator oil 213 is attached to rolling bearing 261, thus rotating stably.

Then, the rotation of rolling elements 271 of rolling bearings 261A and 261B generates passing vibration. When a load changes particularly in a radial direction, the passing vibration provides a large excitation force. This excitation force is relatively large from the frequency of a primary vibration component to the frequency of a secondary vibration component of the primary vibration.

Vibration frequency f of the passing vibration is expressed by the relation between operation frequency N of compressor 1002 and number R of rolling elements 271 (R>1) as the following formula.

f=n·N·R/2 (where “n” is an integer)

Compressor 1002 according to Embodiment 2 operates at three operation frequencies in order to secure the maximum refrigerating capacity and to reduce power consumption. Hermetic container 201 of compressor 1002 has resonant frequency F of 590 Hz. According to Embodiment 2, compressor 1002 operates at three operation frequencies of 18 r/s, 52 r/s, and 80 r/s in order that the resonant frequency is not provided within ranges of ±5 Hz of the frequencies of the primary and secondary vibration components of vibration frequency f of the passing vibration. That is, a predetermined operation frequency of electric element 209 is different from operation frequency N expressed by the following formula.

N=2·F/(n·R) (where n=1, 2)

This condition causes vibration frequency f of the passing vibration to be different from the frequencies of the primary and secondary vibration components of resonant frequency F.

FIG. 8 illustrates a noise profile of compressor 1002 operating at an operation frequency of 52 r/s. Since the resonant frequency is different from the frequencies of the primary and secondary vibration components of vibration frequency f of the passing vibration, a noise at the resonant frequency of 590 Hz is not particularly increased, not increasing the noise level.

According to Embodiment 2, the frequencies of the passing vibration caused by rolling bearings 261A and 261B are different from the resonant frequency in space 201A of hermetic container 201. This arrangement prevents the resonance in space 201A in hermetic container 201 from amplifying noise, thus preventing compressor 1002 from generating a large noise.

According to Embodiment 2, the operation frequency of compressor 1002 is determined so that the frequencies of the primary and secondary vibration components of vibration frequency f of the passing vibration are different from the resonant frequency of hermetic container 201. Alternatively, the number of rolling elements 271 may be predetermined so that the predetermined operation frequency is different from the frequencies of the primary and secondary vibration components of vibration frequency f of the passing vibration.

Compressor 1002 according to Embodiment 2 is of the reciprocating type, but is not limited to this. Bearings 261A and 261B may be applied to compressors of arbitrary types (e.g., rotation type, scroll type, slanting-plate type) including a rolling bearing provided at a bearing of a shaft

The present invention is not limited to Embodiments 1 and 2.

INDUSTRIAL APPLICABILITY

A compressor according to the present invention is prevented from generating large noise, and is applicable to a compressor used for a refrigerating apparatus, such as an air conditioner or a refrigerator-freezer.

Reference Numerals

101 Hermetic Container

103 Refrigerant

109 Electric Element

111 Compression Element

121 Shaft

141 Cylinder Block

151 Bearing

161 Rolling Bearing

171 Rolling Element

1001 Compressor 

1. A compressor comprising: a hermetic container having resonant frequency F; a compression element accommodated in the hermetic container, the compression element being operable to compress refrigerant; an electric element accommodated in the hermetic container, the electric element including a shaft rotating as to drive the compression element at a predetermined operation frequency; and a rolling bearing accommodated in the hermetic container, the rolling bearing supporting the shaft rotatably, the rolling element including a plurality of rolling elements, wherein the predetermined operation frequency of the electric element is different from operation frequency N expressed by a following formula: N=2·F/(n·R) where n=1, 2 and R is a number of the plurality of rolling elements.
 2. The compressor according to claim 1, wherein the rolling bearing comprises a thrust bearing.
 3. The compressor according to claim 1, wherein the rolling bearing comprises a radial bearing.
 4. The compressor according to claim 1, wherein the hermetic container has a space having the resonant frequency F, and wherein the rolling bearing is provided at a node of resonance of the resonant frequency F in the space.
 5. The compressor according to claim 1, wherein the compression element includes a cylinder block providing a compression space arranged to compress the refrigerant therein, and a bearing provided at the cylinder block and supporting the shaft. 